Tentukan persamaan kuadrat yang grafik fungsinya melalui titik A(1, -1), B(2, -3) dan C(3, -11)​

fungsi kuadrat

y = a(x – xp)² + yp

• melalui A(1,-1) dan C(3,-1)

sumbu simetri = xp = (x1 + x2)/3 = (1 + 3)/2 = 2

A(1,-1)

y = a(x – 2)² + yp

-1 = a(1 – 2)² + yp

a + yp = -1 … (1)

• melalui B(2,-3)

-3 = a(2 – 2)² + yp

yp = -3

a + yp = -1

a – 3 = -1

a = 2

rumus fungsi kuadrat

y = 2(x – 2)² – 3

y = 2(x² – 4x + 4) – 3

y = 2x² – 8x + 5